This invention relates to an arcless fuse which will not produce an arc discharge upon melting.
As shown in FIG. 1, a conventional fuse is formed by passing a linear fusible portion (fuse element) 1 through a glass tube 3 and then by connecting opposite ends of the fuse element 1 respectively to terminals (bases) 5 and 5 provided respectively at opposite ends of the glass tube 3. As shown in FIG. 2, another conventional fuse is formed by interconnecting a pair of blade-type male terminals 7 and 7 by a fuse element 1 and then by putting this portion into a housing 9 made of a synthetic resin.
In these fuses, when an overload current or a short-circuit current flows in a circuit as shown in FIG. 3(A), Joule heat J is generated in a localized portion of the fuse element 1 as shown in FIG. 3(B), and when the heat reaches a melting point, the fuse element is fused, and part of the fused portion is vaporized and dissipated as shown in FIG. 3(C). In the conventional fuse, at the time of this dissipation, an arc discharge was sometimes produced in a metal vapor 11 in the atmosphere, so that the current was not interrupted, but flowed. Thus, an arc discharge is almost always involved when the fuse is melted, and in the case of the low-voltage, small-current arc discharge, it fades away to natural extinction, and then the circuit is interrupted.
Although the conventional fuses are so designed that the circuit can be interrupted immediately after the fuse element 1 is melted and dissipated, the current continues to flow during the time when an arc discharge is produced as described above. Therefore, the circuit is not interrupted, so that the purpose of protection is not achieved, and besides there is a possibility that a malfunction is caused in a precision equipment, such as a computer, by an abrupt voltage change developing at the time of an arc discharge.
Furthermore, in the conventional fuses in which the fuse element 1 is dissipated, the glass tube or the housing may be broken, and in some cases this invites an undesirable situation.